Life arose on Earth independent of any influence from space

This first possibility is pretty quickly dismissed by everyone other than creationists.

Earth is not special in a cosmological sense. Earth is not a separate entity somehow set apart from the universe, it is a miniscule part of the universe.

Earth is comprised of debris from space, having been formed as part of the accretion disk that swirled around a newly born star we’ve conveniently named the Sun.

The Sun (and consequently Earth) are second-generation celestial objects. Apart from hydrogen and possibly some trace parts of helium and lithium formed in the Big Bang, every other atom in every single molecule on Earth originated in the fiery heart of a previous generation of stars.

Life arose on a planet that was the result of natural processes in the depths of space, so in some way, panspermia played a part.

The building blocks of life arrived from space

The use of the term “precursor” in the definition of panspermia makes the concept quite broad. In other words, Earth need not be “seeded with life” (either deliberately or via happenstance), it could simply be that the emergence of life was facilitated by the arrival of celestial ingredients on comets and meteorites.

This might sound far fetched at first, but it’s actually quite plausible when you consider that during the Late Heavy Bombardment our planet was inundated with…

…models predicted that an oblique impact could give rise to nitrogen-containing hydrocarbon rings, the major structural component of RNA’s nitrogenous bases… more violent collisions could power the creation of long-chain carbon molecules like those that form the backbone of many amino acids…

Experiments have also shown that the conditions experienced in deep space allow for the natural formation “dipeptides – linked pairs of amino acids.” Space, it seems, is a veritable play-pit full of the Lego blocks required to build life.

As impressive as this seems, life would have to survive for millions to hundreds of millions of years for panspermia to directly seed life on Earth, making this form of panspermia highly unlikely but not strictly impossible.

An experiment at the University of Kent has shown a small percentage of algae can survive an impact at 6.93 kilometers per second, so life could arrive on the back of a cataclysmic comet impact.

Scanning electron microscope image of the diatom frustule

Just last week, researchers at the University of Sheffield announced they’d collected atmospheric samples from the stratosphere above England. To their surprise, they found the damaged remains of what looks remarkably like a diatom, a form of algae.

Because such particles have no known way of reaching this height and can only stay aloft for a few hours, they speculate that these diatoms have come from comet or meteorite dust.

Skeptics have suggested the diatom is far more likely to be a contaminant from the balloon or from lower in the atmosphere, picked up as the balloon rose. As diatoms such as this one are thought to be a recent evolutionary development (ie, within the last 250 million years), it is not likely this is a sample of extraterrestrial life that’s been drifting around frozen for billions of years.

The experiment needs to be independently repeated, as if this controversial finding is correct, then Earth is being continually “seeded” and has been for billions of years. Although this seems extraordinary, it wouldn’t be the first time science has turned out to be stranger than science fiction, but the mostly likely outcome is that this is a false positive.

To put this experiment in context, the collection was conducted at 22-27 km above Earth’s surface (70,000 to 88,000 ft). Commercial airliners fly at roughly 9 km or 30,000 ft, so repeating this experiment in a controlled manner won’t be easy.

The following image is of a high-altitude balloon bursting at roughly 33 km, giving you a good idea of just how far up this collection occurred.

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4 thoughts on “Panspermia”

I think all three possibilities, and a little more besides, would account for the vast varieties of life on Earth…
and that tardigrade looks like an ant wearing a Halloween costume. See all the folds there… 🙂
Fascinating article as always.

That first scene in Prometheus gets my vote. That would be possibility 4: Otherworldly engineers Intentionally brought life to Earth solely to baffle members of the intelligent species that would eventually rise to dominance.

You’re baiting me… and it’s working… ha ha… Thing is, if there had been Erich Von Daniken style alien engineers tampering with our genes we’d see it in the phylogenetic record (which in many ways is better than the fossil record). Rather than slow, steady branching adaptations, we’d see a stark break where “new code” was introduced.

Actually, that’s a strike against #3 as well, as if Earth was seeded with anything other than the most primitive and archaic of organisms, we’d see that as a break/disruption in our branching genetic tree. And conversely, if Earth was continually seeded with the most primitive and archaic organisms from space, we’d see evidence of that as well (multiple starting points at different times in different locations). Life is predatory, so latecomers wouldn’t be welcome, but given what we know of how microbes swap organisms we’d see some imprint on the genetic record. What we see is slowly branching diversity that is in harmony with Natural Selection.